This invention relates to a vibration transducer unit according to the preamble of claim 1.
Vibration transducers can be used for example in saddle or bridge transducers for acoustic guitars, double bass and violin by means of which the vibrations of the strings are converted to electric signals. They are generally mounted under the saddle of the guitar or to the bridge of double bass and violin. They consist of a transducer part with electromechanical material such as elastic electret bubble film, piezoelectric crystals or polymers and electrically conductive electrode layers, as well as a connection cable, by means of which the signals are taken to a separate preamplifier.
In U.S. Pat. publication No. 5,319,153 a piezoelectric transducer for instruments is presented. Therein a strip-formed polyvinylidene fluoride (PVDF) film is used as an active electromechanical material. A connection cable is connected to the transducer part by soldering.
A drawback with vibration transducer units according to the prior art is their complicated structure and high price. When the preamplifier part and the transducer part are placed separately, a connection cable is needed between them. This causes extra costs and the connection cable often causes electrical interference especially if it has to be substantially long. If the electromechanical material used is film-like material, like PVDF rendered into piezoelectric, or elastic electret bubble film with permanent electric charge, the transducer must be very close the preamplifier. This is because this kind transducers have relatively low capacitance compared to standard cables capacitances. Additionally it is difficult to place a separate preamplifier in an electric guitar, double bass or violin. Furthermore, the transducer part and the preamplifier have to be protected by means of separate shields, in order to avoid mechanical damage and electrical interference.
The aim of the present invention is to remove the drawbacks of the prior art technique and to achieve a vibration transducer unit, which is small and compact, and by means of which additional interference can be avoided. In the solution according to the present invention the preamplifier and the transducer part are, according to the attended claims, integrated into one unit. A connection cable between the transducer part and the preamplifier is not needed. As a result a very compact unit is achieved including both mechanical and electrical protection of said unit.